Demystifying Calories: Already There, and Miles to Go

There are three good reasons to write about calories right now. First, the FDA just took action to regulate calorie labeling in chain restaurants. Second, colleagues just published yet another peer reviewed paper probing the mysterious depths of the enigmatic calories.

Third, and most important, if your Thanksgiving was anything like mine, you just had a close encounter with a particular horde of the little devils- and enjoyed every minute of it. I hope so.

Considering that calories are a unit of heat, it’s amazing how much energy is expended trying to shed light on a subject that is only as cryptic as we choose to make it. Personally, I choose not to make it cryptic at all.

The perennial debate, propagated yet again in the new paper, is whether (a) calories count, and (b) a calorie is a calorie. My reliably erudite answers are (a) duh; and (b) hell yeah!

I think the questions are silly. And no matter how perspicacious one is (or feigns to be), there is simply no illuminating answer to a silly question.

The calorie is literally, exactly, and only, a measure of heat, or energy. Specifically, the calorie, per se, is the energy required to raise the temperature of one cubic centimeter of water one degree Celsius at sea level. We generally are invoking the kilocalorie when we speak of food, and use “calorie” as shorthand. The kilocalorie is the stored energy required to raise the temperature of one liter of water just that much under just those conditions.

The debates, or from my perspective pseudo-debates, about the relevance of calories emanate from two serious fallacies: the first is that for calories to count, counting calories must be the most important way to control weight; and the second is that if the quantity of calories matters, the quality must not. Both of these are nonsense.

An analogy is the best way to discredit them as such. Let’s think of fuel, a tank, and an engine.

A gallon, after all, is a gallon. I have not seen that issue debated. It’s a standard measure of volume. It just is what it is.

However, I trust we all agree that “a gallon of what” matters when filling up a tank. The fuel needs to be the right fuel for a given car, for instance. All cars run on closely related varieties of fuel, just as all Homo sapiens run well on variations of the same basic dietary theme: wholesome foods in sensible combinations. But people and cars vary. Some cars need high test, some don't. Some people need more protein, some need less.

But in both cases, it of course matters what the fuel is. That in no way obviates the relevance of quantity: the volume of a gallon, the gallons per tank.

The nature of the engine also matters. Any of us who owns a car considered fuel efficiency when making the purchase. Does variation in fuel efficiency mean a gallon ISN’T a gallon? If one car goes 15 miles on a gallon, and another 45- doesn’t that make the gallon suddenly mysterious?

No; it just means engines differ. In almost exactly the same way, human metabolism varies. Some of us need more fuel to go any given distance, some of us need less. Such variations are traceable, to one degree or another, to variations in our resting energy expenditure, in turn related to variations in our genes, our gene expression, and our intestinal microbes.

In a way most of us understand without any real effort, the quantity of fuel; the size of the tank; the kind of fuel; and the engine all matter. If the kind of fuel and particular engine are fixed, the relevance of volume is clear. Put too little fuel in the tank, and you run out of gas before you get where you’re going- no matter how “good” the fuel, or efficient the car.

Put too much fuel in the tank, and you either flood the tank, the engine, or the driveway. Volume matters. A gallon is a gallon.

But, just as obviously, if you fix the volume, and the engine, then the quality of the fuel discernibly matters. Put in a gallon of poor quality, diluted fuel- and the car will run badly, and less far. Put in the same gallon of high quality fuel well matched to the engine- and the car will perform much better.

Finally, fix the quantity and quality of fuel, but vary the engine- and its relevance is equally obvious. Put the same gallon of fuel into a Hummer or a Prius, and very different trips will result. The trips differ- but a gallon is still a gallon.

The only good questions about any of this are: why do I care, and why should you? Because seemingly good answers to fundamentally silly questions can be dangerously distracting. Consider again the recent FDA action.

I favor calorie labeling, because making somewhat informed decisions is generally better than being utterly clueless. Meaning no offense, most Americans are utterly clueless about calories- demonstrated in every study assessing the average citizen’s capacity to estimate the calorie content of this or that.

So again, clued in is generally better than clueless. Ignorance is not really bliss; it’s the illusory calm before the inevitable storm. I’ll take a clue, thank you very much.

But calorie labeling may greatly exaggerate the relevance of calories. Consider the work of Pulitzer Prize winner, Michael Moss, for instance. Moss is the most recent, if not the first, to detail the skillful, sophisticated work of the food industry designing foods that maximize the number of calories it takes for us to feel full. Those famous “100-calorie” snacks do not seem to help much with total calorie, or weight, control. True, they provide only 100 calories at a time- but most of them are junk foods that propagate appetite, induce almost no satiety, and leave you craving more. FDA calorie labels could, inadvertently, lead people to fewer calories in the guise of smaller portions of junky foods. Nothing good will come of that.

Ideally, then, the at-a-glance information would address not just the quantity of calories, but also their quality. That certainly can be done. Such a measure could, should, and in at least one case does incorporate various factors related to satiety. By maximizing the satiety quotient of foods, which is closely related to overall nutritional quality, the number of calories it takes to feel full can be minimized. This is crucial, because the best way to control the quantity of calories you consume without going hungry- is to improve the quality of those calories.

Calorie labeling is better than no calorie labeling, but not nearly as good as labeling that captures both quantity and quality. Yes, calories count- but counting calories is tedious and unnecessary, if you instead get the big picture right: wholesome foods, in sensible combinations. Yes, of course, a calorie is a calorie just as a gallon is a gallon. But fuels vary, and engines vary- and they matter, too.

I care about this, because I care about using what we know to add years to life and life to years. The more time and energy we devote to questioning answers that are little less than self-evident, the less of our collective wherewithal is left to answer genuinely important questions.

I am constantly mystified at how mystifying we pretend calories can be. For a measure of heat, our debates on the topic shine stunningly little light. If our quest to demystify calories involved only meaningful questions, we would have already been there, done that. Only by posing silly questions and ignoring the obvious relevance of fuel type, fuel amount, tank size, and engine function- do we propagate our pseudo-confusion, and lumber along…with endless miles to go.

-fin

David L. Katz, MD, MPH, FACPM, FAC

Director, Yale University Prevention Research Center; Griffin Hospital
President, American College of Lifestyle Medicine
Editor-in-Chief, Childhood Obesity

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